1. Field of the Invention
The invention relates in general to a display, and more particularly to an adjustable-viewing-angle LCD.
2. Description of the Related Art
With the advantages of low radiation, compactness and slimness, liquid crystal display (LCD) has gained a wide popularity. Due to the features of higher brightness and wider viewing angle, thin film transistor (TFT) LCD is particularly popular among high-level products. A conventional TFT LCD comprises a backlight module, an upper polarizer, an LCD panel and a lower polarizer, wherein the LCD panel is disposed between the upper polarizer and the lower polarizer. When backlight module is disposed beneath the lower polarizer, the light transmission line of the upper polarizer and that of the lower polarizer are perpendicular to each other. Besides, the LCD panel comprises an upper substrate, a lower substrate and a liquid crystal layer, wherein the upper substrate comprises a common electrode, a color filter, an upper alignment film and a black matrix while the lower substrate comprises a number of the scan lines, a number of data lines, a number of storage capacitors, a number of TFTs, a number of pixel electrodes and a lower alignment film. Besides, a partition is used to maintain the fixed interval between the upper substrate and the lower substrate so that the liquid crystal layer is sealed within the fixed interval between the upper substrate and the lower substrate.
Along with the advance in science and technology, modern people have more opportunities to use an electronic product with LCD, e.g., mobile phone, PDA or notebook computer, in public places. Take the notebook computer for example, when using a notebook computer, the viewing angle design of a conventional LCD cannot protect the privacy of the user, and the frame displayed on the LCD can be easily viewed by a bystander in a squint direction. To protect modern people's needs of privacy, the LCD narrow-viewing-angle technology has thus come to the fore.
Referring to both FIG. 1A˜1B, a side view when a conventional LCD at a narrow-viewing-angle mode and a side view when a conventional LCD is a wide-viewing-angle mode are shown. LCD 10 at least comprises an LCD panel 13 and a polymer dispersed liquid crystal (PDLC) device 11, wherein the PDLC device 11 comprises an upper glass plate, a lower plate, liquid crystal molecules and macromolecules. The liquid crystal molecules and the macromolecules are sealed between the upper substrate and the lower substrate. As shown in FIG. 1A, when a voltage is applied to the PDLC device 11, n0, the refractive index of the short axis of the liquid crystal molecules in the PDLC device 11, is equal to the refractive index of the macromolecules enabling the PDLC device 11 to be at a transparent state. Meanwhile, a parallel backlight 12a originating from a backlight module will directly project onto the LCD panel 13 through the PDLC device 11 enabling the LCD 10 at a narrow-viewing-angle mode. That is to say, only the viewer who views the LCD 10 from the front can see the frame displayed on the LCD panel 13; anyone who views the LCD 10 in a squint direction can see the frame displayed on the LCD panel 13.
As shown in FIG. 1B, when no voltage is applied to the PDLC device 11, ne, the refractive index of the long axis of the liquid crystal molecules in the PDLC device 11, does not be equal to the refractive index of the macromolecules, so the PDLC device 11 is at a scattering state. Meanwhile, the parallel backlight 12a will become the non-parallel backlight 12b after passing through the PDLC device 1, while the non-parallel backlight 12b will be projected onto the LCD panel 13 enabling the LCD 10 being at a wide-viewing-angle mode. That is to say, the viewer can see the frame displayed on the LCD panel 13, no matter the viewer views the LCD 10 from the front or in a squint direction. Therefore, the user can determine the LCD 10 being at the wide-viewing-angle mode or the narrow-viewing-angle mode by alternating the PDLC device 11 between the transparent state and the scattering state.
The backlight provided to the LCD 10 is normally from a backlight module. However, present luminous technology of backlight module is still unable to provide real parallel backlight. Although the LCD 10 is already at the narrow-viewing-angle mode shown in FIG. 1A, the user cannot really protect personal privacy and maintain data security. When the backlight projected onto the LCD panel 13 is not real parallel backlight, a bystander still can see the frame displayed on the LCD panel 13 when viewing the LCD 10 in a squint direction. When the PDLC device 11 is at a scattering state, part of the parallel backlight 12a will be reflected by the PDLC device 11, so as to greatly reduce the brightness of the LCD 10 and to influence the operating quality of the LCD 10 severely.